Genetic material tracked down in fossilized droppings / DNA remnants give insight into habits of extinct animals
Using the most modern techniques in molecular biology, Max Planck researcher Svante Pääbo has succeeded for the first time in obtaining parts of the genetic material of a long-extinct animal species from the remnants of its droppings. In conjunction with Hendrik Poinar from the Zoological Institute at the University of Munich and with other colleagues, Pääbo has tracked down and isolated intact DNA from the giant sloth. These vegetarian animals, which were the size of an elephant and lived on the ground, inhabited North and South America until some 10,000 years ago. In a cave near Las Vegas, Nevada, researchers found deep layers of about 20,000-year-old, dried ground sloth dung which served as the source for investigations.
The team of scientists report on their success, which colleagues all over the world consider as an important milestone in the examination of extinct species, in the current issue of the U.S. journal Science (Vol. 281, 17 July 1998). DNA could thus far not be isolated from the feces of extinct animals. The reason for this was recently revealed by a careful analysis: In nature, a chemical reaction takes place in dried dung which creates additional crosslinks between the DNA molecules. Once such Maillard products have developed, the genetic material can no longer be analyzed with conventional methods. But, as Svante Pääbo believes, these crosslinks at the same time protect the DNA from complete destruction. Yet if the scientists treat the ground sloth dung with N-phenacylthiazolium bromide, the crosslinks break open again and the DNA can be analyzed.
Not only its DNA can be found in ground sloth dung but also genetic material from plants the animal fed on. "Though we will never be able to revive extinct species," Pääbo emphasized, "we can at least partially reconstruct their lifeforms and feeding habits." According to investigations, plants from at least eight families from grasses and mustards to mint and mallow were part of the ground sloth’s diet.
Since fossilized remains of feces are often found at excavation sites, numerous further insights could be gained in the future with this new molecular-palaeontologic method. Pääbo even hopes to throw light on Neandertal life in this manner: Before long, he wants to examine 45,000-year-old Neandertal feces from a cave near Gibraltar. He could thus not only be able to explain kinship with modern man more exactly than before; he even hopes to learn what feeding habits this early human had and what parasites plagues him.
Journal
Science